ABSTRACT Vascular dementia (VaD) is common in patients after a stroke or after a series of mini-strokes and results from several mechanisms, one of which involves injury to blood vessels supplying deep white matter (WM) of the brain resulting in silent, multifocal, brain microinfarcts, vascular dysfunction, decrease in cerebral blood flow, and cerebral parenchymal cell damage. Extensive WM damage such as vacuolization, rarefaction, and demyelination in the periventricular region have been reported in patients with VaD. There is a critical need to develop therapeutic strategies for VaD that identify and target key pathophysiological events driving axonal/WM damage and cognitive deficits. The therapeutic effects of Vasculotide, an Angiopoietin-1 mimetic peptide, in VaD have not been investigated. Our preliminary in-vitro studies show that Vasculotide treatment can dose dependently increase axonal outgrowth in primary cortical neurons (PCN). In male retired breeder rats subjected to a multiple microinfarction (MMI) model of VaD, Vasculotide treatment initiated at 24 hours after MMI, significantly decreases axonal/WM injury and improves long term cognitive outcome. In a novel and clinically relevant approach, based on our robust preliminary data, we propose to use Vasculotide for the treatment of MMI induced VaD in male and female middle-aged rats (10-12 months old). We seek to develop Vasculotide as a therapeutic agent to decrease vascular dysfunction and axonal/WM injury, decrease inflammatory responses, attenuate glymphatic dysfunction and improve cognitive outcome. By affecting gene regulation, microRNAs (miRs) are involved in most biological processes and act as molecular rheostats that fine-tune and switch regulatory circuits governing tissue repair, inflammation, hypoxia-response, and angiogenesis. Elucidation of the role of miRs in VaD pathogenesis, and identification of key miRs that can potentially serve as therapeutic targets in VaD are lacking. We hypothesize that Vasculotide treatment induced vascular and axonal/WM remodeling; anti-inflammatory responses and cognitive recovery are mediated via modulation of key miRs and their target gene expression. Therefore, we propose three highly integrated and longitudinally designed Specific Aims. In Aim 1, we will perform dose-response studies and investigate the safety and long term cognitive outcome of Vasculotide treatment in middle-aged, male and female rats subject to MMI model of VaD. In Aim 2, we will investigate the therapeutic effects of Vasculotide on vascular remodeling, axonal/WM remodeling, synaptic plasticity, inflammatory responses and glymphatic waste clearance pathway in middle-aged rats subject to MMI. In Aim 3, using ?gain or loss? of brain miR-145 and miR-124, we will test whether Vasculotide treatment induced therapeutic effects after MMI in rats are mediated via the miR-124/Interleukin-6 and miR-145/Aquaporin-4/ATP-binding cassette transporter A1 (ABCA1) signaling pathways. The long-term objective of this R01 application is to develop a novel treatment for VaD.